1. Field of the Invention
The present invention relates to a receptacle cage, and more particularly to a receptacle cage with a detachable front collar facilitating robust EMI shielding when the cage is mounted onto a printed circuit board with the front boot extending out of a window of a panel.
2. Description of the Prior Art
Historically, electrical and opto-electric modules have been connected to printed circuit boards with solder pins. Conventional approaches for soldering the pins to the circuit board include reflow soldering and hand soldering. Although solder reflow is an effective technique for electrically connecting a module to a circuit board, the heat required to achieve reflow tends to be detrimental to heat sensitive components within the module, such as plastic optical components which tend to warp or otherwise distort at high temperatures. Furthermore, to ensure that modules are capable of withstanding the environmental conditions associated with reflow soldering, the industry utilizes high temperature materials that add cost to the modules. Since most modules will be used in more moderate climates (e.g., an air-conditioned office building), the modules are therefore “over-engineered” simply to ensure that they can withstand the reflow soldering process.
To avoid exposing the module to harsh conditions during reflow soldering, often electronic modules are hand soldered instead to a printed circuit board. The need for hand soldering, however, dramatically increases the cost of system comprising such modules.
Aside from the problems associated with soldering the module to the circuit board, there is the added inconvenience that, if a single module fails on a circuit board, which may support many such modules, the entire circuit board must be removed for service.
Therefore, there is a need for a solderless connection of a module to a circuit board. To this end, several pluggable module designs and standards have been introduced in which a pluggable module plugs into a receptacle which is electronically connected to a host circuit board. For example, a well-known type of transceiver developed by an industry consortium is known as a gigabit interface converter (GBIC) or serial optical converter (SOC) and provides an interface between a computer and a data communication network such as Ethernet or Fibre Channel. These standards offer a generally robust design which has been well received in industry.
Although these conventional pluggable designs have been used successfully in the past, they tend to be unsuitable for miniaturization which is an ever-constant objective in the industry. It is desirable to miniaturize transceivers in order to increase the port density associated with the network connection, such as, for example, switch boxes, cabling patch panels, wiring closets, and computer I/O. Recently, a new standard has been promulgated and is referred to herein as the small form factor (SFF) standard which specifies an enclosure height of 9.8 mm and a width of 13.5 mm and a minimum of 20 electrical input/output connections. In addition to miniaturizing the module, it is also desirable to increase its operating frequency. For example, applications are quickly moving from the sub-gigabit realm to well over a gigabit. Conventional pluggable module configurations, however, cannot meet these parameters.
Miniaturizing a module while maintaining or even increasing its operating speed, presents a number of design problems particularly in applications in which data transmission rates are high, e.g., in the range of 1-10 Gbs (Gigabits/second). Of particular concern is reducing electromagnetic interference (EMI) emissions. Due to FCC regulations, there is a need not only to minimize the EMI emissions of the module, but also to contain the EMI emissions of the host system in which the module is mounted regardless of whether a module is plugged in to the receptacle. In conventional designs, this EMI shielding was achieved by using conductive spring-loaded door which was capable of swinging shut and closing the receptacle when the module was removed. Conventional receptacles also had spring clips to ground the receptacles to the bezel opening of the host system. Providing space for spring-loaded doors and spring clips on the receptacle tends to be problematic if not impossible in miniaturized configurations. Additionally, the small size presents problems in dissipating heat from the module and incorporating traditional mechanisms for ejecting and retaining the module and for electrically connecting the module to the host circuit board.
U.S. Pat. No. 6,517,382 issued to Flickinger on Feb. 11, 2003 discloses A receptacle for a pluggable module which includes a housing having a front, a back wall, a top wall, a bottom wall, and side walls and defining a cavity for receiving a module. The bottom wall has a bottom opening to receive a receptacle connector, and the front has a front opening to receive the module. The walls of the housing are made from a conductive material. A plurality of elongated members extend down from the housing past the bottom wall. The elongated members are adapted for electrical connection to a host circuit board such that the walls of the housing are electrically connected to the host circuit board. As shown in FIG. 1, a front portion is designed to extend through a window of a panel which was disclosed in the original drawing. The front portion is provided with a plurality of resilient fingers such that those fingers can electrical be electrically connected to the inner edge of the winder so as to provide an EMI shielding.
A small form-factor pluggable transceiver (SFP transceiver) provides a link between an electronic transmission line and an optical transmission line as a bi-direction optical-electronic converter. The SFP transceiver is mounted on a printed circuit board of a host system device via a high-speed connector. Then SFP transceiver and the connector are received in a receptacle cage to avoid EMI.
U.S. Pat. No. 7,347,711 issued to Bianchini on Mar. 25, 2008 discloses a fiber optic connector release mechanism. The fiber optic connector release mechanism is used to release a transceiver module from a cage assembly includes a pivoting bail that operates a slide plate on the transceiver module. The locking mechanism comprises a locking projection on an underside of the module housing which mates with an aperture in a flexible locking tab on an underside of the cage. When the release mechanism is actuated, a flexible lifting tab on the slide plate is urged upward by a trailing edge of the locking projection on an underside of the module housing, which in turn moves the locking tab on the cage upward, thereby disengaging the locking tab from the locking projection.
During manufacturing, the side portion is too small to use spot-welding to attach the side portion to the cage body. The reliability of the EMI shielding provided by the cage cannot be ensured.
Hence, an improved receptacle cage is needed to solve the above problem.